Cirsium barnebyi S. L. Welsh & E. Neese

Cirsium barnebyi occurs from the southern Rocky Mountains of southwestern Wyoming, northeastern Utah, and northwestern Colorado.

Perennials, 30–50 cm; caudices and woody taproots. Stems 1–few, erect, gray-tomentose or glabrate; branches few, above middle, ascending. Leaves: blades oblong-elliptic, 10–35 × 2–7 cm, strongly undulate, margins shallowly to deeply lobed, lobes 8–15 pairs, linear-lanceolate to broadly triangular, closely spaced, spreading, coarsely spinose-dentate or cleft into 2–5 spine-tipped divisions, main spines 3–5 mm, faces densely gray-white-tomentose; basal usually present at flowering, winged-petiolate; principal cauline becoming sessile and progressively reduced distally, bases decurrent as spiny wings to 5 cm; distal cauline usually much reduced, less lobed. Heads 1–20+, borne singly or clustered at branch tips, in leafy, ± corymbiform arrays. Peduncles 0–4 cm. Involucres ovoid to hemispheric or campanulate, 1.7–2 × 1.5–2 cm, loosely arachnoid on phyllary margins or glabrate. Phyllaries in 6–9 series, imbricate, ovate (outer) to linear-lanceolate (inner), entire, abaxial faces with narrow glutinous ridge; outer and middle appressed, spines ascending to spreading, stramineous, 2–7 mm; apices of inner often flexuous, narrow, flat, entire, spineless, glabrous. Corollas lavender to pink-purple, 18–28 mm, tubes 7–9 mm, throats 4–8 mm, lobes 5–11 mm; style tips 3.5–5 mm. Cypselae tan to brown, 5–5.5 mm, apical collars colored like body, narrow; pappi 15–23 mm.

Cirsium barnebyi, or Barneby's thistle, is a North American plant species native to the Rocky Mountains of the western United States. It grows in juniper woodlands, sagebrush scrub, etc., at elevations of 1,600–2,600 m (5,200–8,500 ft). It is reported from 6 counties in 3 states: Rio Blanco and Garfield Counties, Colorado; Uintah, Carbon and Duchesne Counties, Utah; and Carbon County, Wyoming.

Cirsium barnebyi is a sparsely-branched perennial herb up to 60 cm (24 in) tall, with a woody taproot. Leaves are oblong to elliptic, up to 35 cm (14 in) long, undulate (wavy), lobed with sharp spines along the edges. Flower heads 1-20, borne at the top of the plant or on the tips of the branches. The phyllaries (modified leaves around the base of the heads) bear sharp spines. Flowers are lavender to pinkish-purple.

Cirsium barnebyi là một loài thực vật có hoa trong họ Cúc. Loài này được S.L.Welsh & Neese mô tả khoa học đầu tiên năm 1981.